How to convert steam quantities to water

[norseman8]

I have a steam humifidier in a new building under construction that uses 1800 pounds of steam per hour. The steam generator is fed from a reverse osmosis water tank. How much RO water is required in gallons per hour?

 

[Istre]

If I've read the question correctly, you should need a feedrate of 1800 lbm/hr to make up the outgoing 1800 lbm/hr of steam. Now, this says nothing about the amount of startup water required to fill the system and related piping, but to provide 1800 lbm/hr in a correctly designed system you'd need 1800 lbmH20/hr to replenish the outgoing steam.

Assuming feed water is at 1 atm and about 70F, it should be about 216 gallons an hour. Of course, if you have any losses in the piping systems you could raise your requirements, and if the feedwater is at wild pressures or temperatures you could see some different water densities.

Take this info with a grain of salt. As I said, I don't know your entire system and am just going on the fact that you need to replenish 1800 lbm of steam/hr.

 

[Montemayor]

norseman8:

Istre is exactly right. A simple mass balance around your vaporizer shows this.

However, this is assuming no accumulation or a bleed-off stream. And in the real world, you always require a constant bleed off on the vaporizer in order to purge out any solids or other contaminants that make it into the vaporizer with the Reverse Osmosis product. No matter how "pure" you think your water is, you will require some excess over the theoretical amount of 1,800 lbm/hr. Istre is saying the same thing indirectly, but he's not being as forceful in stating the need for having extra capacity of water designed into the expected feed rate to the vaporizer. Without any further basic data, I would allow for 20-25% more water fed to the vaporizer.

I hope this helps you out.

Art Montemayor
Spring, TX

 

[rmw]

To to

http://www.katmarsoftware.com

and download a freeware calle Uconeer.

This will do the conversion from lb/hr to gpm, if you put in the necessary paramters.

Then, all you have to consider is the amount of your blowdown, if any, as recommended by montemayor, add it to it, and there you are.

Art, the combination of words "pure water" is an oxymoron, aren't they?

rmw

 

[25362]

To rmw, do you mean it in the sense that present-day water is so contaminated that pure and water would be incongruous or contradictory terms, as in the "wisest fool in Christendom" ?

 

[quark]

You can calculate vaporizer blow down rate by [TDS of water)*water flow rate/Allowable TDS in vaporizer].

For example, if your RO water has 50 ppm TDS and as you may not be operating your vaporizer above 300PSI then you may have to add 50/3500 = 1.43% to your total flowrate. Then there comes condensation losses.

Quality of steam may not be a big problem at the humidifier end if you have proper condensate trapping system. At the most you may not have to desuperheat it.

We generally use the limit of 5ppm hardness to indicate commercial zero quality.

Pure water may be an oxymoron as it is a polar solvent. An experiment conducted in the past proved that high purity water can even dissolve glass a bit.

Nevertheless, there are many varieties of water with various purities, that are even redundant, as far as life is concerned.

 

[rmw]

No, I meant in the sense that quark explained it.

Nature doesn't like a vacuum, and water with no impurities is a vacuum that it will fill, even from glass, if necessary, as pointed he pointed out.

rmw

 

[Montemayor]

To rmw:

Yes, you employed the correct phrase in describing what I didn't state outright. quark also pounds on the same subject: regardless of how much we want to believe that our water is immaculate, the bitter truth is that it indeed is the "Universal" solvent. Sooner or later, everything winds up in water - even life matter.

Thanks for reinforcing the harsh engineering reality surrounding the purity of industrial (or any other source) water.

Art Montemayor
Spring, TX

 

[GenB]

just use the simple way,
8.33 lbs of steam makes one GL. 'can't go wrong with it.
if you can do this and want accurate reading, buy a water meter and read it/ clock the meter. water meters are cheap.
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